Divergent results in radial immunodiffusion with antisera differing in precipitation properties with respect to individual immunoglobulin subclass. I. The antigen factor.

Two bovine IgG subclasses were used as reference antigens to study subclass influence on radial immunodiffusion results with total bovine IgG. In combination with some of eight anti-bovine IgG sera tested the use of the same antiserum with one subclass furnished values which were about twice as high as values obtained with the other subclass. It is concluded that immunoglobulin determinations by radial immunodiffusion are influenced by the chosen reference antigen and by subclass ratios in the samples tested. The composition of immunoglobulin subclass mixtures for testing antisera used in radial immunodiffusion is discussed.